GTS Mod 4 Difficult

Compressor Bleed Valve System

• The compressor bleed valve system unloads the compressor during start and up to 13,000 RPM or 94% engine speed.
• The system unloads the compressor by bleeding air from the compressor's fifth and tenth stages.
• The engine can operate at low speed ground idle, reducing engine speed to save fuel and reduce noise during ground operations.

Speed Sensitive Valve

• The speed sensitive valve controls the compressor bleed valve system.
• The valve causes the compressor bleed valves to open if low speed ground idle or engine shutdown are selected.
• The speed sensitive valve repositions the speed sensing valve, opening the port which directs 14th stage air onto the bleed air valve piston heads when the engine is running at 94% RPM or more.

Compressor Bleed Valve Operation

• When the engine is running at 94% RPM or more, the compressor bleed air valves are forced closed.
• When the engine is operating at less than 94% RPM, the speed sensing valve flyweights position the sensing valve to stop 14th stage air acting on the 5th and 10th stage bleed valves, allowing compressor air to force open the 5th and 10th stage bleed valves.

Compressor Bleed Surge Control System

• Compressor bleed surge control systems are used on multi-spool engines.
• The system relieves the engine of excess air at low engine RPM during normal low speed operations, including engine start.
• When engine cranking first begins, air will flow inward through the compressor bleed valve to the inlet of the rear compressor, relieving part of the windmilling load of the front compressor.

Compressor Bleed Valve System Components

• The system consists of four pneumatically operated bleed valves located on the compressor fifth stage and tenth stage.
• The system also includes a speed sensitive valve mounted on the forward face of the accessory gearbox and all necessary plumbing and manifolds.
• The excess air is ducted overboard when the bleed air valves are open.